Antidistortion device



April 30, 1935.

w. KAUTTER ANTIDISTORTION DEVICE Filed Sept. 25, 1931 INVENTOR WOLFGANGKAUTTER BY M Q, g

ATTORNEY Patented Apr. 3Q, 1935 I h v Smite Artist enact ANTmrs'ronrioNDevice Wolfgang Kautter, Eerlin-Charlottenburg, Germany,'assignor toSiemens & Halske, Aktiengesellschaft, Siemensstadt, near Berlin, Germanya corporation of Germany 7 Application'september 25, 1931, Serial No.564,999

r v In Germany October 2, 1930 3 Claims. (Cl. 179-171) In thetransmission of the voice, music and the the desired curve-shape isobtained. However, like by radio ithappens that the high frequenthismeans in practice that the aggregate imprescies are unfavorably treated,sion of volume is diminished inasmuch as part of Accordingly it is anobject of the present inthe energy is destroyed or by artificially andin- 5 vention to overcome such difficulties and several tentionallyreducing the gain. Another way 5 Ways and means by which these resultsare acwould be toraise artificially the gain for the highcomplished areshown by the accompanying drawer frequencies. 7 ing wherein: V Anarrangement to produce this result is shown Fig. 1 shows the resonancecurve of a receiving by Fig. 3, wherein the plate circuit of tube 5comdevice; prises the battery 2, an ohmic resistance 3 and 10 Fig. 2shows a desired form of frequency curve an oscillation circuitconsisting of an inductance for the receiver amplifier; coil 4 and acondenser E. Coupling with the tube Fig. 3 illustrates one system whichtends to 6 forming the next'stage of the amplifier is proproduce afrequency'curve oi the character shown vided from the point i by way ofa condenser 8 by Fig. 2; I a to the grid electrode 9 of the tube 6. 15

Fig. 4 illustrates a modification of the system The oscillation circuitcomprising inductance of Fig. 3; and 1 H and capacity 5 is sodimensioned that the ascend- Fig. 5 illustrates a still further andpreferred ing branch of its resonance curve falls inside modification ofFig. 3. higher frequencies so that the gain of the ampli- Referring nowto the drawing, the conditions fier becomes lilgewise greater for higherfrequen- 20 which tend to produce unfavorable treatments cies, with theresult that the desired distortion of of the higher frequencies willbecome more apthe curve-shape is secured. parent by referring to theresonance curve of I There is, however, one demeritin this type of varrangement, which is that while greater gain is 5' n t s C v the abscssae dica s the freobtained for the higher frequencies, it is rather quy F a d the ordinates ind at f r xa p e difficult to adapt the gain toany prevailing conthe potential E at t d of the a d b ditions with areasonable degree. of exactness." Th rri r W v pp in the mi l f theAnother disadvantage resides in the circumstance reSOnanOe Curve,therefore, p Velathat the inductance 4, which is usually iron-cored,

tively Sp the highest Iwtential at the grid-1 is passed by the platedirect current. This, on the 30 The side-band quencies to! and 202result in one hand, means that this choke-coil 4 must be lowerpotentials because of the droop of the resomade of gomparatively largeproportions m fiance much as the currents flowing through the plate Thefact that the Side-bands are 1935 f circuit are liable to be of rathergreat strength;

ably treated, and Consequently also the higher and furthermore theinductance value of the frequencies, results in a distortion inreproducchoke-coil and thus also the resonance point are tion. One,therefore, is compelled to so dimengreafly d d nt up n th strength ofthe plate S1011 the receiver pp a fl Particularly the direct current,which may be different according audio frequency part thereof, that thispreferent ki diti tial treatment of the high frequencies is avoided-According to this invention the desired correc- 40 Hence, the frequencycurve" of the amplifier should tion of t distortion of di frequency i tb be chosen as shown, for instance, in Fig. 2, where arrangement isobtained by s0 proportioning the abscissae indicate the frequencies Fand the -designing t coupling means t t t transmisordinates theamplification factor or gain V of sion of t frequency b is i ed ipluralthe arrangement. From this figure it can be ity of frequency-bandgroups 45 clearly seen that at points between 4000 and 5000 o embodimentaccording t invention cycles the amplification of the apparatus must bet produce this result is shown in th modifica.. raised considerably tionillustrated by Fig. 4. In this arrangement Such an artificially produceddistortion of the t coupling of t grid i it of t b H ith so p fi u v maybe r u ht a ut i d the plate circuit of tube in is effected by way n w yStarting fr m an plifi r in of the capacitive channel comprising theconpractically uniform amplification throughout the denser 2 and by ay fth inductive h l, entire band, all that has to be done is to diminishcomprising the choke coil 3 Condenser g and th a p fi a n for t lower pt his may inductance is are connected in parallel and are beaccomplished by suitable circuit means so that brought to the gridcondenser M, which has ne 55 t end terminal thereof connected with thegrid l5 of the tube H. The plate alternating current potential of tube Iis taken off at the plate circuit resistance It. The capacitive branchI2 is united with the end of resistance l6 near the plate. The inductivebranch is united directly at I! with the same resistance l6, which has,most preferably, the form of a potentiometer resistance. In such acircuit arrangement the coupling ofhigh frequencies is of maximum value,While that of the low frequencies is variable. By suitably setting thecoupling of the inductive branch the relationship between the gainforthe lowfrequencies and thato j the high frequencies may be regulatedwith thelr'esult that a characteristic curve of the kind shown in Fig. 2as being desirable is obtained.

V Inasmuch as the low pitches are governing so far as the subjectivesound volume impression is concerned, it will be seen that the aggregatevolume decreases with increasing correction of distortion. Although allcorrections of distortion no matter of whatnature, are predicated uponthe circumstance that the changes of amplification of an outfit can notbe fully utilized particularly for the low pitches, which are mostdecisive so far as the volume is concerned, it will be seen that suchdecrease in the aggregate sound volume nevertheless makes an unfavorableimpression. However, the latter is avoidable by the manner in which thelow frequencies are coupled, i. e., that of the inductive branch is madeconstant, while only that of the capacitive branch is varied. This isshown in Fig. 5.

Referring now to Fig. 5, the grid circuit of the tube H is incouplingrelationship with the plate circuit of tube I 0 by way of thecapacitive branch l2 and the inductive branch l3, The plate resistancesconsist of two series-connected resistances I8 and I9. At the junctionpoint 20 between the resistors l8 and IS the inductive branch of thecircuit is connected, whereas the capacitive branch I2 is variablyunited with the resistance l8. This latter variable connectionpreferably is in the nature of a potentiometer. Inasmuch as the couplingof the inductive branch,,which is decisive for the subjective volume asit carries the lower pitches, is constant, it follows that the aggregateimpression of the volume of the sound will not experience any changes ifby shifting the contact 2| the amplification of the high frequenciesbeing predominantly transmitted by way of branch [2 is varied.

The great advantage which the scheme according to the present inventionoffers resides in the fact that it. is feasible to insure a correctionof distortion of the audio frequencies, quantitatively, this having beenfeasible also in the case of the circuit scheme shown in Fig. 3. Anotheradvantage of a constructional nature is that no direct current flowsthrough the'choke-coil 13. As a result, thischoke-coil l3 may be chosenof rather small proportionsand its inductance preserves 7 an invariablevalue inasmuch as it experiences no biasing magnetization at all by theaction of the direct current.

The invention and its scope is by no means restricted to the embodimentsshown by way of example in Figs. 4 and 5 since naturally, it is alsopossible to make both the inductive as well as the capacitive branchvariable in coupling, as will become at once apparent to any one skilledin the art to which the invention relates.

Having now described the'invention, what is claimed and desired tosecure by Letters Patent of the United States is the following:

1. A system for correcting distortion at high frequencies comprising aplurality of amplifying devices, means for capacitively connecting theoutput of one amplifying device with the input of the other amplifyingdevice, a resistance forming part of the direct current output circuitof the first amplifying device, and a parallel combination of inductanceand capacity elements having one terminal of each connected to theresistance element and the other terminal to the capacity couplingconnecting the amplifying devices.

2. An amplifying device comprising a plurality of vacuum tubeamplifiers, a plurality of parallel electric paths including inductanceand capacity elements connecting the output of one vacuum tubeamplifying device with the input of the other vacuum tube amplifyingdevice capacitively and inductively and capacitively, and a resistorconnected in the direct current output path of the first amplifier andadjustably connected to a terminal point of at least one of theinductance and capacity elements.

3. In a distortion correcting amplifier system, a plurality ofamplifying devices, a resistance element connected in the output circuitof the first amplifying device, a capacity element conlow frequency anda high impedance path to high a frequency, and a second capacity elem ntinseries with each of said capacity and inductance elements fortransferring output energy from the first amplifying device to thesecond of said amplifying devices. a

WOLFGANG KAUTTER.

